A standards determination work related to a next-generation communication scheme of a wideband code division multiplexing access (W-CDMA) scheme, a high speed downlink packet access (HSDPA) scheme, a high speed uplink packet access (HSUPA) scheme and the like, that is, a standard determination work related to an LTE (long term evolution) (E-UTRA) scheme is under progress in 3GPP, which is a group aiming to standardize.
As a radio access scheme of the LTE scheme, an OFDMA (Orthogonal Frequency Division Multiplexing Access) scheme has been employed for a downlink, and an SC-FDMA (Single-Carrier Frequency Division Multiple Access) scheme has been employed for an uplink.
The OFDMA scheme is a multi-carrier transmission scheme in which a frequency band is divided into a plurality of narrow frequency bands (sub-carriers) and data is loaded on each sub-carrier and is transmitted. According to the OFDMA scheme, the sub-carriers are densely arranged on a frequency axis while being orthogonal to the frequency axis, so that high-rate transmission can be achieved, and frequency use efficiency can be expected to be improved.
The SC-FDMA scheme is a single-carrier transmission scheme in which a frequency band is divided for each terminal and a plurality of terminals transmit data using different frequency bands. According to the SC-FDMA scheme, since inter-terminal interference can be simply and effectively reduced and a variation in transmission power is small, the SC-FDMA scheme is advantageous in terms of lower power consumption of a terminal, expansion of coverage, and the like.
In an LTE mobile communication system, in both a downlink and an uplink, one to two or more resource blocks are assigned to a user equipment so that communication is performed. Here, the resource blocks are shared by one to two or more user equipments in the mobile communication system.
A base station device is configured to decide a user equipment, to which a resource blocks is to be assigned, among one to two or more user equipments, for each subframe (1 ms in the LTE scheme) (such a process is called “scheduling”).
In the downlink, the base station device is configured to transmit a shared channel signal to a user equipment, which has been selected through the scheduling, by using one to two or more resource blocks.
In the uplink, the user equipment selected through the scheduling is configured to transmit a shared channel signal to the base station device by using one to two or more resource blocks.
In the mobile communication system using the shared channel as described above, it is necessary to perform signaling of a user equipment, to which the above-mentioned shared channel is to be assigned, for each subframe (1 ms in the LTE scheme).
In the LTE scheme, a control channel used in such signaling is called PDCCH (Physical Downlink Control Channel) or “downlink L1/L2 Control Channel (DL-L1/L2 Control Channel)”.
For example, “downlink scheduling information”, “uplink scheduling grant” and the like are mapped to information on the physical downlink control channel. In addition, the above-mentioned downlink scheduling information or uplink scheduling grant is also called “DCI (Downlink Control Information)”. The above-mentioned downlink scheduling information or uplink scheduling grant corresponds to information for performing signaling of a user equipment to which the above-mentioned shared channel is to be assigned.
Meanwhile, in cellular phones, radio astronomy, satellite communication, air and sea radar, earth resources survey, and a wireless LAN, which are mobile communication systems using a radio wave, frequency bands to be used are generally separated from one another in order to prevent mutual interference.
Furthermore, for example, a plurality of mobile communication systems use frequency bands assigned to cellular phone systems, and frequency bands to be used in the mobile communication systems are separated from one another. That is, the mobile communication systems using radio waves separates frequency bands to be used from one another, thereby preventing inter-system interference.
Here, when a transmitter radiating a radio wave has not transmitted a signal at a frequency determined in advance, or when it has transmitted the signal at the frequency determined in advance but has transmitted an unnecessary wave (or an interference wave) with power larger than a permitted value to a frequency band different from a frequency band of an own system, it may have a significant adverse influence on other systems with different frequencies.
In order to avoid the above-mentioned adverse influence, for a user equipment in a mobile communication system, an operation for reading broadcast information from a base station device and then transmitting an uplink signal based on the scope of “Receive before transmit” has been defined.
In the “Receive before transmit”, the “receive” indicates an operation for receiving the broadcast information, and the “transmit” indicates an operation for transmitting the uplink signal.
The scope is based on the assumption that in relation to a base station device, a provider providing the mobile communication system appropriately operates the mobile communication system under the monitoring of administration of each country, but a user equipment is not monitored because it is a radio communication terminal owned by a general user.